Clear the fd from pending events after it's been processed

src/iomux_epoll.c

@@ -183,6 +183,8 @@ again:
             fd->callback(mux_, fd, events);
             //be sure not to use fd after the callback, it might been removed.
 
+            mux->pending_events[i].data.ptr = NULL;
+
             event_cnt++;
         }
     }